There are two alternatives for carrying out the machining of crankshaft ends.
There are environments wherein high production demands prevail, such as for example the automobile industry. In these sectors, dedicated transfer machines are mainly used, which have high effectiveness but very low flexibility for adapting to changes in the characteristics of the crankshafts to be machined. Therefore, high production is achieved at the expense of low flexibility with regard to changes in crankshaft machining.
However, in other sectors where machining centres are used, a high degree of flexibility is reached which allows fast assimilation of changes in the characteristics of the crankshafts to be machined but at the expense of low productivity.
A transfer machine is a machine wherein a part is transported from station to station, being machined at each station with units on either side of the part, a specific operation of the crankshaft end, in such a manner that the crankshaft ends have been machined in their entirety.
In the machining centre one end is firstly machined, changing the tool to carry out the different machining operations; the part is rotated using a plate to position it facing the other end of the crankshaft and, changing the tool, the machining operations are carried out at the other end.
In both cases, once the crankshaft has been machined, it must be unloaded and dismounted in order to subsequently load and mount a new crankshaft. The duration of this process, while shorter than that of machining, is by no means negligible and should be taken into account in the design of the machining machine.
At present, an evolution has taken place in the automobile sector which, while maintaining the same high levels of production, requires the flexibility inherent to low-production solutions in order to adapt the product to market demands.
The solution to this flexibility and productivity problem should also take into account that machining of the crankshaft ends is not symmetrical, i.e. the machining of the first crankshaft end or spike end is carried out in less time than the machining of the second crankshaft end or flange end. The relationship between both times is such that machining of the spike end can be carried out in 75% of the machining time of the flange end. This leads to the existence of numerous downtimes due to the disparity in machining times for each of the ends of a crankshaft. Additionally and as mentioned earlier, the moment in which the unloading/dismounting and loading/mounting tasks are carried out must be taken into account in order to minimise their impact on the total duration of the process.
In the state of the art, no solution is known which allows ad hoc machining of each crankshaft, in such a manner that productivity is not substantially reduced with respect to transfer machine productivity and downtimes are minimised.